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CBSE Class 12 · 2001 · Delhi Compartment · Aldehydes Ketones and Carboxylic AcidsVery Short Answer

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Give one chemical test to distinguish between acetaldehyde and benzaldehyde.

Answer: Fehling's test: acetaldehyde gives red Cu₂O; benzaldehyde (aromatic) does not. (Iodoform also works: CH₃CHO positive.)

Solution

Warm with Fehling's solution: aliphatic CHCHO reduces it to red CuO precipitate; benzaldehyde leaves it blue (aromatic aldehydes do not reduce Fehling).
(Alternative: iodoform test — positive only for acetaldehyde.)

CBSE Class 12 Board · 2001 · Delhi Compartment · Subjective

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